Question

I wrote the following code and got no output. Here is the code

var a1 = undefined;
var a2 = 5;
if(a1 > a2)
    alert(1);
if(a1 < a2)
    alert(2);
if(a1 >= a2)
    alert(3);
if(a1 <= a2)
    alert(4);

There was no alert box that came up which means that the if statements resulted in false. Can I know the reason?

Answer 1

JavaScript tries to casts the value of x to number using ToPrimitive (@RobG). Since x is undefined, this will return NaN which compares false to any value. So it will always return false.